Automaton

From publisher blurb:

The Automatons were originally the shock troops of an ancient spacefaring race. Built in the construction facilities of gigantic, automated battleships, Automatons serves as front line soldiers whenever this now extinct species had to defend itself or felt the need to expand its interstellar territory. While little is known about this mysterious race, vague clues gleaned from the rare interactions people have had (and survived) with their technology suggest that these mechanical creatures eventually malfunctioned, turned on, and destroyed their masters.